بررسی فراسنجه‌های زیستی شته مومی کلم تحت تیمارهای مختلف روی کلزا

Among oilseed plants, canola (Brassica napus L.) has an important role and due to its desirable characteristics, it's considered as a point of hope for supplying the oil needed in the country. Cabbage aphid, Brevicoryne brassicae (L.) is one of the most important pests of this plant, which through direct feeding or transmission of pathogenic viruses can significantly limit the production of the crop. Today environmental problems caused by irregular application of chemical compounds and the side effects which have on biological cycles, is one of the reasons to the approach of using biostimulants. In this study, the effects of humic acid and PGPR (Pseudomonas fluorescens NBTR168+ Azotobacter chroococcum NBTAzt2 + Azospirillum brasilense NBTAzoof) were investigated on life table parameters of B. brassicae. The experiment was done in greenhouse conditions and in completely randomized design with 40 replication. To evaluate the effects of studied treatments on the life history parameters of aphid, experiment was carried out using clip cages established on leaves of potted canola plants. After 24 hours, adult aphid and all nymphs except one nymph were removed. Each cage was monitored daily until the maturity of the aphid. After maturity, daily observations were followed until each female aphid died. Data were analyzed based on the age-stage, two-sex life table and the method described by Chi (1988). The means and standard errors of life table parameters were determined using the bootstrap technique with 100,000 resampling. The bootstrap method is embedded in the computer program TWOSEX-MS Chart. The results showed, there was no significant difference in the nymph period of B. brassicae among studied different fertilizer treatments. However, tested treatments significantly influenced longevity, reproductive period and fecundity of this aphid. Moreover the reproductive period of B. brassicae on plants treated with humic acid, PGPR and PGPR+humic acid were significantly lower than those on plants without fertilizer treatments (control) The lowest and highest number of nymphs produced per female was calculated on PGPR and treatment control (28. 40 & 44.44 nymphs) resepectively. Based on the analysis results of population growth parameters, the lowest Gross reproductive rate (GRR) of this aphid was obtained in of humic + PGPR treatment and its highest in control. Also, the net reproductive rate (R0) of this pest was significantly higher in the control treatment compared to other fertilizer treatments. The lowest values of Intrinsic rate of increase (rm) and Finite rate of increase (λ) of this aphid were significantly in PGPR treatment (0.181 and 1.198 day, respectively) and the highest in control were calculated (0.202 and 1.224 day-1 respectively). Therefore, it can be concluded that PGPR and Humic acid + PGPR treatments can induce canola resistance to cabbage aphid.